Polycarbonate mixtures

ABSTRACT

Mixtures of 10 to 95 parts by weight of polycarbonate of recurring units   WHERE:

United States Patent Serini et al.

[ June 17, 1975 POLYCARBONATE MIXTURES lnventors: Volker Serini,Krefeld; Hugo Vernaleken, Krcfeld-Bockum; Wolfgang Cohnen, Krefeld, allof Germany Bayer Aktiengesellschaft, Leverkusen Bayerwerk, GermanyFiled: Sept. 26, 1973 Appl. No.: 400,757

Assignee:

Foreign Application Priority Data Oct. 5, 1972 Germany 2248817References Cited UNITED STATES PATENTS 9/1961 Goldberg 260/47 X 11/1966Caldwell ct al. 260/860 8/1957 Kim 260/860 l/l969 Wulff ct a1 260/860Primary Examiner-Morris Liebman Assista n1 ExaminerT. Pertilla Attorney,Agent, or FirmLawrence S. Pope ABSTRACT Mixtures of 10 to 95 parts byweight of polycarbonate of recurring units with 90 to 5 parts by weightof homopolycarbonate with recurring units and where Y Cl, Br.

6 Claims, N0 Drawings POLYCARBONATE MIXTURES BACKGROUND OF THE INVENTIONDt-OS (German Published Specification Nos.) 2,063,050 and 2,063,052describe polycarbonates based on bis-(3,5-dimethyl-4-hydroxyphenyl)-methane, 2,2-bis-( 3 ,5-dimethyl-4-hydroxyphenyl propane anda,a-bis-(3,5-dimethyl-4-hydroxyphenyl)- p-diisopropylbenzene. Incontrast to the previously known polycarbonates, for example those basedon 2,-

2-bis-(4-hydroxyphenyl)-propane (bisphenol A, BPA),

these polycarbonates are highly resistant to saponification, i.e.,resistant to hot aqueous alkali and to hot aqueous mineral acid.Furthermore, they have glass transition temperatures of about 200C whichlie substantially above that of EPA-polycarbonate of 150C. Hence, theycan be employed in many fields in which previously known polycarbonates,such as BPA- polycarbonate, could not be used. However, it has beenfound that some of the properties of the new polycarbonates are not yetsatisfactory. Thus, the impact strength of the new polycarbonates stillleaves something to be desired. Furthermore, the melt viscosity isrelatively high, which is a disadvantage for thermoplastic processing.Additionally, the melt viscosity increases on thermoplastic processingin the presence of atmospheric oxygen. Additionally, the fireresistance, especially at low wall thicknesses, is not as good as thatof BPA-polycarbonate.

SUMMARY OF THE INVENTION It has now been found. surprisingly, that thesaid disadvantages of the polycarbonates based on bis-(3,5-dimethyl-4-hydroxyphenyl)-methane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane and a,a-bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene may be eliminated bymixing these polycarbonates with BPA-polycarbonate which optionallycontains cocondensed 2,2-bis(3,5-dibromo-4-hydroxyphenyl)- propane and2,2-bis-(3,5-dichlor0-4-hydroxyphenyl)- propane. The products of theinvention, therefore, are mixtures of 10 to 95 parts by weight ofpolycarbonate with recurring units.

with 90 to 5 parts by weight of homopolycarbonate of recurring units orof copolycarbonate with recurring units and where there are at least twounits derived from the bisphenol A per halogenated unit.

DETAILED DESCRIPTION As stated previously the present invention includesmixtures of IO to 95 parts by weight of polycarbonate based onbis-(3,5-dimethyl-4-hydroxyphenyl)- methanc,2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)propane anda,oz-bis-(3,5-dimethyl-4-hydroxyphenyl)-pdiisopropylbenzene with 90 to 5parts by weight of BPA-polycarbonate which, optionally, containscocondensed 2,2-bis-( 3 ,5-dibromo-4-hydroxyphenyl propane and2,2-bis(3,5dichloro-4-hydroxyphenyl)- propane. As will be seen from theexamples polycarbonates having especially advantageous properties areobtained from mixtures of 30 to 90 parts by weight of thetetramethyl-substituted bisphenol polycarbonates with 70 to parts byweight of the BPA- polycarbonates.

Polycarbonates from the abovementioned tetramethyl-substitutedbisphenols are homogeneously miscible in all ratios with theBPA-polycarbonate and with the copolycarbonates of EPA and2,2-bis-(3,5-dibromo-4- hydroxyphenyl)-propane or2,2-bis-(3,5-dichloro-4- hydroxyphenyl )-propane.

This was unexpected since small differences in the structure of polymersfrequently suffice to cause a complete or at least partialincompatibility in mixtures. An example of such polymers with onlyslight structural differences and which cannot be mixed homogeneously inall ratios are polystyrene and poly-a-methylstyrene. The polycarbonatemixtures of the invention, because of their homogeneous miscibility, arecompletely transparent and in each case only show one glass transitiontemperature. Example 2 lists some of the mixtures according to theinvention, with their glass transition temperatures,

The mixtures of this invention show substantially better stability tosaponification than is to be expected from the mixing ratio of theinitial polycarbonates (see Example 3).

As compared to the homopolycarbonates from the tetramethyl-substitutedbisphenols mentioned, the mixtures of the invention show the advantagesof a substantial improvement in the impact strength of test specimens(see Example 8) and improved ease of flow of the melt.

The admixture of even relatively small proportions of BPA-polycarbonateprevents the increase in the solution viscosity or in the melt viscosityof the said polycarbonates based on tetramethyl-substituted bisphenolsduring thermoplastic processing in the presence of atmospheric oxygen(see Example 4). This is a great advantage since on multiple extrusionin the presence of atmospheric oxygen, as can frequently not be avoidedin practice (incorporation of glass fibers, stabilizers, dyestuffs,pigments and other additives; reprocessing and the like), a constantviscosity of the melt is thus maintained, which ensures uniformproduction of the molded articles on repeated extrusion.

If the BPA-polycarbonate, which is related to the polycarbonate mixturesaccording to the invention, contains co-condensed2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane (TBBPA) or2,2-bis-(3,5-dichloro- 4-hydr0xyphenyl)-propane (TCBPA), the advantagesdescribed above remain preserved but additionally the fire resistance isincreased. The BPA-polycarbonate when co-condensed with TBBPA or TCBPAshould contain at least two units derived from BPA per unit derived fromTBBPA or TCBPA. It is surprising that substantially smaller amounts ofhalogen suffice for the mixtures than for BPA-polycarbonate in order toachieve a certain fire resistance, for example Class SE-O according toUL Subj. 94 (see Example 5). Generally as little as about 4% by weightof bromine and 10% by weight of chlorine based on the total weight ofpolycarbonate will suffice to achieve Class SE-O or SE-l for mixturescontaining up to by weight of the tetramethyl-substituted bisphenolpolycarbonate. Here one is apparently dealing with a synergistic effect.The CH groups, in the o-position to the carbonate groups, of thepolycarbonates from the tetramethyl-substituted bisphenols mentioned,are in themselves disadvantageous to the fire resistance (compareExample 5). However, in mixtures with polycarbonates which containnuclear-halogenated bisphenols, these methyl groups produce asubstantial improvement in the fire resistance (compare Example 5),which consists both of a reduced smoldering time after exposure to theflame and also ofa reduced tendency to drip. It is to be assumed thatthe synergistic effect is based on the ease of abstraction of H atoms atthe CH groups on the nucleus, with the formation of radical positions onthe polycarbonate chain.

On incorporation of glass fibers, the polycarbonate mixtures of theinvention show improved behavior, relative to BPA-polycarbonate, onclimatically controlled storage; thus a decrease in impact strength isbarely perceptible even after very long storage at 40C and 96% relativehumidity. The appearance of such polycarbonate mixtures containing glassfibers is also improved relative to corresponding BPA-polycarbonatescontaining glass fibers. While, for example, BPA- polycarbonate with 20%of glass fibers appears turbid and whitish-grey, the mixtures accordingto the invention containing additionally 20% of glass fibers are almosttransparent or only slightly opaque. Hence a further subject of theinvention are the polycarbonates mixtures of the invention containingadditionally up to 40 parts by weight of glass fibers referred to theweight of the mixture of polycarbonates.

Two further improvements of the mixtures according to the inventionrelative to BPA-polycarbonate may additionally be mentioned. Thestructural viscosity of the mixtures according to the invention isparticularly high so that they are very suitable for the extrusion oflarge hollow articles (see Example 6). Furthermore, their trackingresistance is better than that of the BPA- polycarbonate (see Example7), which is ofimportance for a variety of uses in the electricalindustry.

The tetramethyl'substituted bisphenol polycarbonates useful in themixtures of the invention are prepared according to the methodsdisclosed in Dt-OS 2,063,050 and Dt-OS 2,063,052 by reacting thebischlorocarbonic acid esters of the corresponding bisphenols or byreacting the corresponding bisphenols with phosgene or with thebischlorocarbonic acid esters of the bisphenols in accordance with thephase boundary condensation process, in the presence of aqueous alkaliand a solvent suitable for polycarbonates, through the addition of atleast 10 mol per cent and up to 200 mol per cent, relative to thebisphenol, of tertiary amine. The subsequent reaction time is chosen sothat the product of the amount of amine (mol per cent) and the reactiontime (hours)exceeds a value of 15. The process may be carried out ineither one step or several steps. For example, the bisphenols aredissolved in aqueous alkali, preferably in sodium hydroxide solution orpotassium hydroxide solution, and a suitable solvent for thepolycarbonate being produced is added.

Suitable solvents of this nature are generally chlorinated hydrocarbons,such as methylene chloride, chloroform and l,2-dichloroethane. and alsochlorinated aromatics, such as chlorobenzene, dichlorobenzene andchlorotoluene. Phosgene is passed into this mixture with vigorousstirring. In the case of bisphenols which, because of their hydrophobiccharacter, do not produce bisphenolate solutions, a suspension isadvantageously employed. The amount of phosgene required depends on thebisphenol employed, the stirring action and the reaction temperature,which can lie between about C and about 60C, and is in general l.l-3.0mols of phosgene per mol of bisphenol. After the phosgenation, which canalso be carried out in the presence of chain stoppers, for example2,6-dimethylphenol, the condensation to give a high molecularpolycarbonate is carried out by adding the tertiary amine, for exampletrimethylamine, triethylamine, dimethylbenzylamine ortriethylenediamine, as the catalyst. The amounts of amine are in general10-200 mol per cent, relative to bisphenols, but preferably 10-50 molper cent are employed.

The polycarbonates manufactured in the manner described above may beisolated according to known processes, for example by separating off theaqueous phase, repeatedly washing the organic phase with water until itis free of electrolyte, and thereafter precipitating the polycarbonateor evaporating off the solvent.

The BPA-polycarbonate suitable for the invention, which include those inwhich the EPA has been cocondensed with tetrabromobisphenol A ortetrachlorobisphenol A. may be prepared by any of those techniques knownin the art. For example, the polycarbonate may be produced from thecorresponding dihydroxy diaryl alkanes and phosgene or the correspondingdiester of carbonic acid, for example, as described in Canadian Pat.Nos. 578,585, 578,795 and 594,805 and U.S. Pat. Nos. 3,028,365 and2,999,835. Other processes contemplated for producing the BPA-polycarbonate include those referred to in Polycarbonates by William F.Christopher and Daniel W. Fox.

The polycarbonate mixtures of the invention can be manufactured bymixing the granules of the starting polycarbonates and conjointextrusion on single-screw or multi-screw extruders. However, they canalso be manufactured by mixing the appropriate polycarbonates insolution, for example, in CH Cl and subsequently evaporating off thesolvent. While with the second kind of mixing complete homogeneity isachieved in every case, it is necessary, in the case of the former typeof mixing, to ensure that the extruder produces a sufficient mixingaction to achieve the completely homogeneous mixing of thepolycarbonates.

The polycarbonate mixtures of the present invention can be convertedinto moldings, films, fibers and coatings. It is possible to mix intothem organic and inorganic reinforcing agents and fillers, for exampleminerals, and also substances producing special effects, pigments,dyestuffs, stabilizers against damage by UV light, heat treatment andoxidation and the like, lubricants, anti-static agents and furtherauxiliaries. They can be employed in numerous fields in which BPA-polycarbonate has also been used. In addition they can, in particular,be used in fields where stability to saponification, a high glasstransition temperature, a high tracking resistance and good structuralviscosity of the melt, also in combination with fire resistance, areofimportance. Thus they can serve, for example, for the manufacture ofpipelines for hot alkaline or acid solutions, of high quality gaskets,of tableware, of articles which can be sterilized by superheated steam,of saponification-resistant coatings and of electrically insulatingarticles of high tracking resistance, and as dielectrics.

The molecular weights (M measured by light scattering) of thepolycarbonates to be used according to the invention are generally above20,000. In the case of the manufacture of the mixtures by a meltprocess, polycarbonates with molecular weights between 30,000 and 80,000are preferably used. If the mixtures are produced via the solutions, themolecular weights may be higher.

The invention may be more fully understood by referring to the examplesthat follow.

EXAMPLE 1 Manufacture of polycarbonate from2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane and its bischlorocarbonicacid ester 22.4 g of sodium hydroxide (0.56 mol) and 22.7 g of2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane (0.08 mol) are dissolvedin 600 ml of water. ml of methylene chloride and 3.0 ml of triethylamine(0.02 mol) are then added while stirring. 49.1 g of thebischlorocarbonic acid ester of2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane (0.12 mol) dissolved in500 ml of methylene chloride, are added all at once to the mixture,while stirring vigorously. The mixture is then vigorously stirred for afurther 2 /2 hours. The process is carried out under nitrogen at 2025C.After the subsequent stirring the batch is worked up. The aqueous phaseis free of bisphenol. The organic phase is diluted with methylenechloride and is then washed twice with 5% strength aqueous hydrochloricacid and thereafter water until free of electrolyte. The polycarbonateis precipitated from the organic phase to yield 59 g of a whiteflocculent polycarbonate, the methylene chloride solution of whichyields a clear, tough, strong film. The relative viscosity of thepolymer is 1.529 (in methylene chloride at 25C, c 5g/l). The averagemolecular weight by light-scattering 171 is 83,000 and the glasstransition temperature is 206C.

EXAMPLE 2 Glass transition temperatures of homogeneous polycarbonatemixtures Polycarbonates of relative viscosity 1; 1.30 (0.5 g/100 ml ofCH Cl solution at 25C) were manufactured in a manner similar to thatdescribed in Example l and as generally described above (as disclosed inDt-OS 2,063,050 and 2,063,052) from 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane, bis-(3,5dimethyl-4-hydroxyphenyl)-methane and a,a-bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropylbenzene. The polycarbonateswere isolated from the CH CI solution as mats by evaporating the solventon metal sheets. The mats were granulated in a beater mill and thegranules were well dried. The resulting polycarbonates were mixed, as aCH Cl solution, with BPA- polycarbonate (11 1.30) in the mixing ratiosshown in the table. Films were spread from the solutions and afterdrying the glass transition temperature was determined on the films bydifferential thermoanalysis. All films were transparent. The granules oftwo of the polycarbonates (see table) were also mixed in the melt withBPA-polycarbonate granules in various ratios, using a twin-screwextruder at 300C. These mixtures, again, were transparent. They showedsimilar glass transition temperatures to the polycarbonates mixed insolution b. Stability of pieces of film, as in a), in strength aqueousHCl at 100C.

Properties of the films Treatment BPA-PC BPA-PC/PCl BPA-PC/PC3 (seetable). 1n the case of all mixtures, only one glass im (h u mixt r mi te transition temperature could be found. 0 500 b u u Table accompanyingExample 2:

Glass transition temperatures of homogeneous polycarbonate mixturesEXAMPLE 4 Determination of the glass transition temperature S f h l(GTT) by differential thermo-analysis. ta 1 lzauon O t 6 p0 ycarbonatesfrom PCl Polycarbonate from 2,2-bis-(3,5-dimethyl4-hydroxyphenyl)-propane PC2 Polycarbonate from bis-(3,5-dimethyl-4-hydroxyphenyl)-methane tetramethyl-substituted bisphenols by admixtureof EPA-polycarbonate The polycarbonate mixtures listed in the table weremanufactured, as described in Example 2, via the melt PC3 Polycarbonatefrom a,a-bis-(3,5-dimethyl-4- in a twin-screw extruder, with access ofair. They were hydroxyphenyl )-p-diisopropylbenzene then repeatedlyextruded on a single-screw extruder at Mixtures of BPA-PC/PCl Mixturesof BPA-PC/PCZ Mixtures of BPA-PC/PC3 prepared in solution (parts GT1prepared in solution (parts GT1 Prepared in solution (parts GTT byweight) (C) by weight) (C) by weight) (C) Mixtures of BPA-PC/PClMixtures of BPA PCIPC3 prepared in the melt at 300C GT1 prepared in themelt at 300C GTT (parts by weight) ("C) (parts by weight) (C) EXAMPLE 3300C, as was the EPA-polycarbonate listed in the ta- Stability ofpolycarbonate mixtures to saponiftcation by ble. After each extrusion,the relative viscosities of the hot aqueous NaOH/HCl polymers weremeasured.

Mixture of BPA-PC/PCl Mixture of BPA-PC/PC3 Polycarbonate BPA-PC PC1 PC320/80 parts by weight 20/80 parts by weight 1 initially 1.302 1.3011.298 1.301 1.299 1 1st extrusion 1.296 1.320 1.316 1.303 1.302 17 2ndextrusion 1.292 1.343 1.335 1.304 1.302 rpm. 3rd extrusion 1.290 1.3711.360 1.300 1.300

Table accompanying Example 4: 1 f (number of extrusion passes) PCI seeExample 2 PC3 set: Example 2 The films were prepared via the C1-1 C1solution, as EXAMPLE 5 described in Example 2.

PC] PC2 see Example 2. u =unchanged, tough, b =brittle, decomposeseasily,

turbid a. Decrease in weight of pieces of film 4 X 5 cm,

Fire-resistant polycarbonate mixtures The polycarbonate mixturescontained in the table were manufactured from polycarbonate granules ona twin-screw extruder, as described in Example 2. The

-100 pm thick, weight 150 to 200mg, in 10% 6O copolycarbonates,containing halogen, used for the strength aqueous NaOH at C.

Weight decrease (mg) BPA-PC/PCl mixture 30/70 parts by weight Treatmenttime (hours) BPA-PC BPA-PC/PC3 mixture 30/70 parts by weight 500completely 0 dissolved 9 the two-phase boundary process using suchamounts of ing resistance was measured on test specimens of thesehalogenated bisphenol A that the copolycarbonates mixtures and also ontest specimens of EPA- and the mixtures manufactured therefrom have thehalpolycarbonate (1 1.30). The results are shown in ogen contentsindicated in the table which follows. the table:

Polycarbonate or PC mixture Tracking resistance according to VDE 0303.part l /9.64 (DIN 53.480/6). test solution F, KBlevel BPA PC 340 VBPA-PC/PCl mixture. 70/30 parts by weight 560 V BPA-PC/PCl mixture.50/50 parts by weight 560 V BPA-PC/PC2 mixture. 70/30 parts by weight560 V BPA-PC/PC3 mixture. 70/30 parts by weight 560 V PC] see Example 2PC2 sec Example 2 PC3 sec Example 2 Table accompanying Example 5:EXAMPLE 8 Bmminc Impact strengths of polycarbonate mixtures, compared PCor PC mixture chlorine 1 Fire test result Wlth thosfi of the Startmgpolycarbonates content. accordin 7, by M f fi UL The polycarbonates oftetramethyl-substituted bisphenols, contained in the table, were mixedwith EPA- BPA-PC 0 1302 SE ll 01 b t h l 0 0 1301 n p ycar onae (see tae) in t e met at C on a PC; 0 1197 n twin-screw extruder. The followingimpact strengths 0 ESE 4 1532 g were measured on test specimens of thehomopolycarp 'C p PC 10 1292 SE n bonates and the mixed polycarbonates.BPAJIBBPA-CPC/PCI mixture, 50/50 parts 4 1.299 SE 0 by weightBPA-TBBPA-CPC/PCZ 3O mixwm 5050 Parts 4 L303 SE 0 Polycarbonate or 17",,Impact strength (cmkplcm y weight PC mixture DIN 53,453BPA-TBBPA-CPC/PC3 mixture. 50/50 parts 4 1.30l SE 0 BPA-PC 1.30 nb 80)by weight PC] L BPA-TCBPA-CPC/PCI PC2 1.30 37 mixture. 50/50 parts [01.295 SE l 35 PC3 130 31 BY WEIGHT BPA-PC/PCI mixtures 50/50 parts byweight 1.30 nb 80) PC 2 sec Hump]c 2 25/75 parts by weight 1.30 nb 80)PC2 sec Example 2 BPA-PCIPC2 mixture PC3 sec Examplc 2 50/50 parts byweight 1.30 nb TCBPA 2.2-his-l3.5-dichloro-4-hydmxyphcnyl)-pr0paneBPA-PCIPCB mi u TBBPA 2.2-bis-(3.5-dibromo4-hydroxyphcnyl)propane 030/70 parts by weight 1.30 nb 80) CPC cupolycarbonate n not classifiedPCl. PC2. PCS as in Example 2 rib not broken EXAMPLE 6 Structuralviscosity of polycarbonate mixtures What IS clalmed 151 l. Polycarbonatemixtures comprising, based on the polycarbonate, 10 to 95 parts byweight of polycarbonate of recurring units:

The table contains the melt viscosities of EPA- polycarbonate and ofpolycarbonate mixtures according to the invention at different speeds ofdeformation.

The polycarbonate mixtures show a substantially P CPS, greaterdependence of the melt viscosity on the speed of deformation than doesBPA-polycarbonates. The 1.. relative viscosity of the polycarbonatesused was 1.30. I

The melt viscosity was determined in a capillary viscometer. CF1

Melt viscosity at 300C (P) P(l 2 sec Example 2 PC2 sec Example 2 EXAMPLE7 CH3 Tracking resistance of polycarbonate mixtures The mixtures listedin the table were manufactured v by mixing polycarbonate granules (11.30) in the b u melt, using a twin-screw extruder at 300C. The trackand90 to parts by weight of l) homopolycarbonate and of recurring units: I

Y Cl,

5. Polycarbonate mixtures comprising, based on the CH1 5 polycarbonate,30 to 90 parts by weight of polycarbonv ate of recurring units:

0. PC O-C- I. CH O (Ll-I CH e I0 i I 4 +--o "my wo e-+- or (2)copolycarbonates of recurring units: i CH o e CH3 where CH CH CH I I IL/-- "..C.

V X -CH -c- -c c- I u A I on; U c CH on, cu,

and V 3 l 3 CH Y I, i

g I n r and 70 to 10 parts by weight of( l homopolycarbonate f 5" 'F 'f"of recurring units:

CH o CH where I s Y Cl, Br CH 0 and wherein there are at least two ofthe former unit per latter unit, and each of polycarbonates in saidmixtures has an average molecular weight, lVI above or (2)copolycarbonates of recurring umts' 2. The polycarbonate mixtures ofclaim 1 wherein C 1 +O X-CJ \.o c l. L x I ll i CH o i -C L J 15 and 3.The polycarbonate mixtures'of claim 1 wherein Y 3 Y I 7 I O C O-C l x;Y/ CH3 OJ and i I where Y Br. Y Cl, Br

Pfolycarbonate mixtures according to claim 1 and wherein there are atleast two of the former unit wher per latter unit, and each ofpolycarbonates ir said mix- CH3 0 tures has an average molecular weight,M above 20,000. X 6. The polycarbonate mixtures of claim 1 containingadditionally up to 40 parts by weight of glass fibers, re- CH ferred tothe weight of the mixture of polycarbonates.

1. POLYCARBONATE MIXTURES COMPRISING, BASED ON THE POLYCARBONATE, 10 TO95 PARTS BY WEIGHT OF POLYCARBONATE OF RECURRING UNITS:
 2. Thepolycarbonate mixtures of claim 1 wherein
 3. The polycarbonate mixturesof claim 1 wherein
 4. Polycarbonate mixtures according to claim 1wherein
 5. Polycarbonate mixtures comprising, based on thepolycarbonate, 30 to 90 parts by weight of polycarbonate of recurringunits:
 6. The polycarbonate mixtures of claim 1 containing additionallyup to 40 parts by weight of glass fibers, referred to the weight of themixture of polycarbonates.